Question about Intel disk formats

From: Edwin P. Groot <epgroot_at_ucdavis.edu>
Date: Thu Jun 21 19:47:52 2001

     What I read on the Web was that the first Shugart 801's could not
read/write DD, no matter what controller was attached to it. However,
later-manufactured 801's could handle both SD and DD.

     Edwin

At 03:07 PM 6/21/2001 -0600, you wrote:
>Tony's right about the Shugart 801's. Drives don't determine the modulation
>technique used to record the data. The "density" refers to the number of
bits
>per linear inch on the track. Since that's really not an adequate measure in
>this context, its sensibly applied analog would be bits per revolution. The
>head/media combination determines the number of flux changes per inch
(fcpi) and
>single-density uses two flux changes per bit, while double density uses
only one
>(not exactly, but close enough). If the drive can manage to swap the flux
>direction quickly enough, which the '801 clearly can, then it's a
double-density
>capable drive, which it is. Confusion arises from the fact that, while
the '801
>can read/write double density, its board-resident "data separator" can't.
Also,
>while the older '901 wasn't commonly used for double density, it could manage
>MFM if one used 250ns of write precomp. The '801 required only 160-180 ns.
>
>Dick
Received on Thu Jun 21 2001 - 19:47:52 BST